Chromosome Chaos
by EvilFuzzy9
Summary: Because genetic analysis is much trickier than you might think, and the author feels continually compelled to play devil's advocate. [spoilers for chapter 700 7]


**Chromosome Chaos**

A _Naruto_ oneshot

By

EvilFuzzy9

* * *

Rating: T

Genre: Family/Sci-Fi

Characters/Pairings: Sarada, Naruto, Suigetsu; [implied SasuSaku, SuiKa]

Summary: Because genetic analysis is much trickier than you might think, and the author feels continually compelled to play devil's advocate. [spoilers for chapter 700 + 7]

* * *

"Why should I go help someone who isn't even my mother?! She's nothing to me! I've let it go unsaid for too long; I don't even know what to believe, anymore...!"

Naruto winced, seeing the tears in Sarada's eyes.

"Aw, geez," he muttered. "This is _really_ not the best time for preteen drama... Can we save this for later, Sarada? Like maybe after we've saved your mom?"

"That's just what I'm saying!" Sarada snapped. "She's NOT my mom! That test... You can't fake results like that!"

"Is that so?" Naruto said, cocking his head to one side. "But I've heard it's more difficult to track maternal lineage than it is to track paternal. 'Cause of the chromosomes, or something."

Sarada blinked. "What?"

"Yeah, you know, chromosomes. Put 'em together to make a strand of DNA? Women are XX, men are XY."

"Of course I know about that," Sarada scoffed. "It's basic genetics."

Naruto did a double take.

"Wait, you really do?! Wow, then maybe you can figure it out for me! I don't really know this stuff all that well, myself..." He gave an apologetic smile.

Sarada sweatdropped.

 _Is... is this guy really the Inestimable Lord Hokage?_ she thought exasperatedly.

Then she shook her head.

"Well, I don't really get what you're trying to say..." she muttered, "...but, yes, as far as chromosomes, women have a combination of XX, while men have XY. So... if you're trying to determine the relationship between, say, a father and son, then it's pretty easy. Since only men have Y chromosomes, you just have to match the son's Y chromosome with the father's Y chromosome."

"Right, right," Naruto said, beaming.

"But that isn't infallible either, from what I know," chimed Suigetsu, walking into the room. "Determining relation through DNA samples... well, overall there are a considerably smaller number of distinct Y chromosomes than X chromosomes, so that sort of comparison is a double-edged sword. A close male relative of the father – like say a brother, or even _his_ father – would share the same Y chromosome as well, or near enough to muddy the waters."

Naruto glowered at Suigetsu.

"And just what do you think you're doing interfering again, you Taka jerk...?"

"Hey, I'm just trying to help," said Suigetsu innocently. "I don't like the idea of that kid there being the product of a fling between Sasuke and Karin any more than she does."

"So you're bargaining already?" Naruto drawled.

Suigetsu replied with a fairly rude gesture.

"Up yours," he said. "I'm trying to make a point."

"But all of that is moot, isn't it?" Sarada interjected. "Because I'm not a son, and I'm not trying to track my relation to my father."

"Right, you're a daughter trying to identify your mother," Naruto said. "And that's tricky, isn't it? X chromosomes are more common, so..."

"But that's not what's used to test maternal lineage, usually," Suigetsu interjected. "Mitochondrial DNA is what they use for that. And normally that gets passed down perfectly, with only very rare mutations."

"So that makes it easier to test?" Sarada said.

Naruto hummed thoughtfully. "I wonder about that..."

"You'd think so, wouldn't you?" Suigetsu said. "But that's just the problem. Mitochondrial DNA is usually identical between mother and child... but that works across multiple generations. Say your great-great-great grandmother had three kids, all girls, and each of those girls had three daughters, and each of _those_ girls had three daughters... all the way down to your generation. It's very likely that all those kids would have identical, or nearly identical mitochondrial DNA.

"Y'see? Near perfect mtDNA matches are possible within as many as **sixteen** generations. People usually stop reckoning immediate relatives after two or three. We're talking about _four or five times_ further back than that. And that test back there was only comparing your and Karin's DNA."

"How far up your family tree can you count, Sarada?" Naruto inquired, seeing where Suigetsu was going. "Your grandparents? Your great grandparents? And how many generations have the hidden villages been around for? Four, five. Six, maybe seven at the most. He's talking about ancestors two or three times as old as Konoha. Who knows how far a person's oats can be sowed in that time..."

Sarada frowned.

"What are you suggesting?" she asked.

Naruto shrugged. "I always was a little suspicious of that hair... pink is pretty close to red, when you think about it. I don't think it's inconceivable that Sakura and Karin could've shared a common maternal ancestor within the last sixteen generations."

Sarada gave Naruto a baleful look. "I find that _highly_ unlikely."

"You could compare my DNA to yours, then!" Naruto said with a laugh. "Me and Karin are both Uzumaki, after all. And me on my mother's side, at that! It's highly possible that she and I would have very similar... what did he call it, mtDNA? Yeah."

Sarada stared at Naruto.

"And if it did match? If Sakura isn't my birth mother?"

A shrug.

"Then Karin's the one who popped you out of her cooch," Suigetsu said. "Although that's annoying in its own way..."

"...also," Naruto added, clapping a hand onto Sarada's shoulder. "Whether or not Sakura's your biological mom, she's still the person who raised you and took care of you all these years. Blood might be thicker than water, but I think the latter is more valuable in the long run."

He grinned from ear to ear.

Sarada sniffed and wiped away her tears.

"...fine. Let's go save her."

"If she really needs saving," said Suigetsu.

"If she really needs saving," Naruto agreed.

* * *

A/N: I'm mildly surprised by the revelation in this latest chapter, I must admit... though I'm also impressed, in another way. I don't think it's too likely Kishi will use any devices like what's presented in this chapter to backpedal that (apparent?) reveal, but you never know. Haha!

Of course, it does also seem possible that Shin's obsession with genes could be setting up for direct contrast with Sakura considering emotional and spiritual bonds much more important than an actual blood relationship. The nitty-gritty of the circumstances around Sarada's birth is still up in the air, either way.

Also, today marks the ninth anniversary of my joining this site.

Christ... How time flies, eh?

 **Updated:** 6-11-15

 **TTFN and R &R!**

– — ❤

EDIT:

PS:

Go see _Jurassic World_. I don't care if that has nothing to do with this fic, fandom, or anything. GO SEE IT. ADFAASDFDFSFDAS.

It is awesome. That is all.


End file.
